Refactor CLI to use flags instead of positional arguments

- Change all commands to use flags (--bucket, --prefix, etc.)
- Add --config flag to backup command
- Support VAULTIK_CONFIG environment variable for config path
- Use /etc/vaultik/config.yml as default config location
- Add test/config.yaml for testing
- Update tests to use environment variable for config path
- Add .gitignore for build artifacts and local configs
- Update documentation to reflect new CLI syntax

internal/cli/entry_test.go

@@ -31,4 +31,20 @@ func TestCLIEntry(t *testing.T) {
 			t.Errorf("Expected command '%s' not found", expected)
 		}
 	}
+	
+	// Verify backup command has proper flags
+	backupCmd, _, err := cmd.Find([]string{"backup"})
+	if err != nil {
+		t.Errorf("Failed to find backup command: %v", err)
+	} else {
+		if backupCmd.Flag("config") == nil {
+			t.Error("Backup command missing --config flag")
+		}
+		if backupCmd.Flag("daemon") == nil {
+			t.Error("Backup command missing --daemon flag")
+		}
+		if backupCmd.Flag("cron") == nil {
+			t.Error("Backup command missing --cron flag")
+		}
+	}
 }